We propose to continue our study of the molecular-level mechanisms that explain the toxicity and pulmonary pathology caused by ppm levels of ozone and nitrogen dioxide. We have chosen first to study the reaction of these toxins with models of lung lipids, since there is clear evidence that much of the damage caused by these toxins is due to free radical reactions and polyunsaturated fatty acids (PUFA) in lipids are known lipid autoxidation, and this is known to cause damage to membranes and ultimately cell death. With ozone, we have been concentrating our attack on methods of distinguishing between the products of ozonolysis (the ozonide) and of radical-mediated autoxidation of PUFA (e.g., conjugated diene hydroperoxides). Our aim is to quantify the amounts of damage by these two mechanisms. We also are probing the mechanism by which ozone (a non-free radical) reacts with PUFA to form radicals. We have shown using a novel and newly-developed electron-spin resonance technique that ozone forms radicals with PUFA even at minus 30 degrees C; we propose extending this method to other types of biomolecules (e.g., polypeptides, thiols, etc.). We also propose a stopped-flow study of the reaction of ozone both in organic solvents and in water with a series of biomolecules. We have shown that NO2 reacts with PUFA in organic solvents entirely and simply as an initiator of autoxidation. However, we find that NO2 initiates autoxidation both by addition to the double bond and by abstraction of doubly allylic hydrogen atoms; this is the first time evidence for the latter process has been reported. We now are directing our study of NO2 to aqueous systems, starting with emulsions of PUFA esters in aqueous buffers. We propose ultimately to study monolayer vesicles, multilayer liposomes, and then biological materials such as rbc.